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CHICAGO POLICE DEPARTMENT
MARINE OPERATIONS TRAINING BULLETIN
VOLUME I, NUMBER I
23 MAY 2006
On 19 May 2006, the Marine Unit Dive Team conducted dive training on Lake Michigan aboard Marine Unit vessel M-7. Two (2) Dive Instructors and four (4) Divers were on board.
The dive site was 1 mile east of the Chicago Harbor Lighthouse in open water. Winds were from the North / Northwest at 8-10 mph, waves were 2-3 foot, maximum depth was 34 ft., water temperature was 51 degrees and the vessel was drifting at a speed of approximately 2-3 mph. The divers equipment included a dry suit, a full face mask (AGA) with wireless communications, a redundant air supply and a Zeagle BCD.
A concrete brick, attached to approximately 60 ft. of line, was secured to the stern of the vessel and dragged on the bottom to act as a sea anchor to slow the vessels drift. Two (2) 12 foot tow lines were attached to the brick for the officers to hold as they were pulled along the bottom.
Three (3) drift dives, with two (2) divers each, were scheduled. The divers were given a dive briefing which included the dive site, water conditions, communications and entry/exit procedures. The Dive Supervisor gave a detailed explanation of the divers position in the water at all times, in relation to the instructor and/or other diver. A diver safety brief was covered and the pre-dive checklist was used prior to entry.
Two (2) drift dives, lasting approximately 20 minutes each, were completed without incident. Divers A and B entered the water for the third and final dive. Approximately 10 minutes into the dive, diver A experienced an equipment malfunction with the CPD Divator MK II Full Face Mask (AGA). The diver was at maximum depth and had just finished checking his air gauge, which showed 2200 lbs. when he heard a loud Pop and the mask began to free flow.
The diver performed a limited check of the mask and the spider straps in an attempt to pinpoint the problem. Unable to stop the mask from free flowing and unable to communicate due to the noise associated with the free flow, diver A swam several feet over to diver B, motioned to his mask and signaled to terminate the dive and ascend. Diver B removed the redundant air supply regulator from the BCD of diver A and placed it in the hand of diver A. Both divers then began a controlled ascent up the tow line.
At approximately 12 ft., diver A decided to stop his ascent and switch to his redundant air supply, rather than wait for his primary air to run out. With diver B holding onto the line with one hand and the BCD of diver A with the other, diver A ripped off his AGA mask and switched to his redundant air supply. As the divers were making this transition, the movement of the vessel had been pulling them up closer to the surface. This change in depth and their inability to dump air during the transition caused an expansion in the remaining air in their BCDs and dry suits, which was increasing their rate of ascent.
The divers surfaced approximately 30 feet behind the vessel, with diver B still holding onto the line and diver A. By holding onto the tow line, diver B actually prevented an uncontrolled ascent the final few feet due to the weight of the concrete brick at the end of the line. The dive instructor made a surface swim from the vessel to the divers and attempted to turn the free flowing AGA mask off by the positive pressure switch. These attempts were unsuccessful. The instructor then disconnected the AGA mask at the quick connect and assisted in fully inflating the BCD of diver A. All three swam back to the vessel under their own power and exited the water. The ending primary air of diver A was 250 lbs.
During the dive debriefing, the top side divers, the instructors and the divers involved determined the rate of ascent was less than desired for the last 12 feet, but far from an uncontrolled ascent. The divers reported they were aware of their ascent, were breathing the entire way and had not held their breath at any time. Both of the divers said they felt no effects of decompression sickness or any other injury. The divers were checked out by the dive instructor, who is also an Emergency Medical Technician, and the preliminary indications were the divers showed no signs of decompression sickness or injury.
Dr. Zenetti of Swedish Covenant Hospital was contacted by cell phone from the vessel. Once docked at the Chicago Marine Safety Station, the divers were taken to Swedish Covenant Hospital as a precautionary measure. Both divers were examined by Dr. Zenetti who determined they showed no signs of injury and were released.
LESSONS LEARNED
It was determined the malfunction on the AGA mask was due to a plastic nut on the regulator, where the hose enters the regulator, which had loosened. The nut had turned back several rotations, causing the free flow.
This type of equipment failure was unknown to any Marine Unit personnel prior to this occurrence.
The remedy for preventing this type of malfunction is to ensure the nut is finger tight during the inspection of the mask, prior to the dive.
Both officers performed the emergency ascent perfectly under real conditions and should be commended.
Both officers remained calm and made the right decisions under stressful conditions.
Thankfully, both officers had just gone through the open water AGA training one week prior and mastered the skills necessary to perform the skills when it was needed most.
Diver A could have continued his ascent to the surface wearing the free flowing AGA. After the fact, it was determined he would have had enough air to make it to the surface safely.
Because of the training the diver knew he could easily switch to his redundant. When he decided to ditch his AGA, he was comfortable, confident and he did exactly as his training taught him.
When diver A switched to his redundant air source, if for any reason there was a failure with the secondary air source, he could have switched back to the AGA which was free flowing, but usable, this is also a skill taught in the Open Water AGA Training course.
Once on the surface, it was important to stop the free flow by disconnecting the mask before the primary tank was empty. This ensured there was enough air left to power inflate the BCD. Otherwise the diver would have had to manually inflate the BCD.
Contact with Dr. Zenetti was initiated by the Marine Unit Training Board, at the beginning of the training, to establish the proper procedures for notifying and transporting an injured diver. Having established this contact prior to an incident helped assisted in calling the doctor on his personal cell phone and making arrangements for him to see the divers.
Checking the Nut to ensure it is finger tight has been included in the Pre-Dive Checklist. The tightness of the nut will be checked by the diver and the tender prior to entering the water.
MARINE OPERATIONS TRAINING BULLETIN
VOLUME I, NUMBER I
23 MAY 2006
On 19 May 2006, the Marine Unit Dive Team conducted dive training on Lake Michigan aboard Marine Unit vessel M-7. Two (2) Dive Instructors and four (4) Divers were on board.
The dive site was 1 mile east of the Chicago Harbor Lighthouse in open water. Winds were from the North / Northwest at 8-10 mph, waves were 2-3 foot, maximum depth was 34 ft., water temperature was 51 degrees and the vessel was drifting at a speed of approximately 2-3 mph. The divers equipment included a dry suit, a full face mask (AGA) with wireless communications, a redundant air supply and a Zeagle BCD.
A concrete brick, attached to approximately 60 ft. of line, was secured to the stern of the vessel and dragged on the bottom to act as a sea anchor to slow the vessels drift. Two (2) 12 foot tow lines were attached to the brick for the officers to hold as they were pulled along the bottom.
Three (3) drift dives, with two (2) divers each, were scheduled. The divers were given a dive briefing which included the dive site, water conditions, communications and entry/exit procedures. The Dive Supervisor gave a detailed explanation of the divers position in the water at all times, in relation to the instructor and/or other diver. A diver safety brief was covered and the pre-dive checklist was used prior to entry.
Two (2) drift dives, lasting approximately 20 minutes each, were completed without incident. Divers A and B entered the water for the third and final dive. Approximately 10 minutes into the dive, diver A experienced an equipment malfunction with the CPD Divator MK II Full Face Mask (AGA). The diver was at maximum depth and had just finished checking his air gauge, which showed 2200 lbs. when he heard a loud Pop and the mask began to free flow.
The diver performed a limited check of the mask and the spider straps in an attempt to pinpoint the problem. Unable to stop the mask from free flowing and unable to communicate due to the noise associated with the free flow, diver A swam several feet over to diver B, motioned to his mask and signaled to terminate the dive and ascend. Diver B removed the redundant air supply regulator from the BCD of diver A and placed it in the hand of diver A. Both divers then began a controlled ascent up the tow line.
At approximately 12 ft., diver A decided to stop his ascent and switch to his redundant air supply, rather than wait for his primary air to run out. With diver B holding onto the line with one hand and the BCD of diver A with the other, diver A ripped off his AGA mask and switched to his redundant air supply. As the divers were making this transition, the movement of the vessel had been pulling them up closer to the surface. This change in depth and their inability to dump air during the transition caused an expansion in the remaining air in their BCDs and dry suits, which was increasing their rate of ascent.
The divers surfaced approximately 30 feet behind the vessel, with diver B still holding onto the line and diver A. By holding onto the tow line, diver B actually prevented an uncontrolled ascent the final few feet due to the weight of the concrete brick at the end of the line. The dive instructor made a surface swim from the vessel to the divers and attempted to turn the free flowing AGA mask off by the positive pressure switch. These attempts were unsuccessful. The instructor then disconnected the AGA mask at the quick connect and assisted in fully inflating the BCD of diver A. All three swam back to the vessel under their own power and exited the water. The ending primary air of diver A was 250 lbs.
During the dive debriefing, the top side divers, the instructors and the divers involved determined the rate of ascent was less than desired for the last 12 feet, but far from an uncontrolled ascent. The divers reported they were aware of their ascent, were breathing the entire way and had not held their breath at any time. Both of the divers said they felt no effects of decompression sickness or any other injury. The divers were checked out by the dive instructor, who is also an Emergency Medical Technician, and the preliminary indications were the divers showed no signs of decompression sickness or injury.
Dr. Zenetti of Swedish Covenant Hospital was contacted by cell phone from the vessel. Once docked at the Chicago Marine Safety Station, the divers were taken to Swedish Covenant Hospital as a precautionary measure. Both divers were examined by Dr. Zenetti who determined they showed no signs of injury and were released.
LESSONS LEARNED
It was determined the malfunction on the AGA mask was due to a plastic nut on the regulator, where the hose enters the regulator, which had loosened. The nut had turned back several rotations, causing the free flow.
This type of equipment failure was unknown to any Marine Unit personnel prior to this occurrence.
The remedy for preventing this type of malfunction is to ensure the nut is finger tight during the inspection of the mask, prior to the dive.
Both officers performed the emergency ascent perfectly under real conditions and should be commended.
Both officers remained calm and made the right decisions under stressful conditions.
Thankfully, both officers had just gone through the open water AGA training one week prior and mastered the skills necessary to perform the skills when it was needed most.
Diver A could have continued his ascent to the surface wearing the free flowing AGA. After the fact, it was determined he would have had enough air to make it to the surface safely.
Because of the training the diver knew he could easily switch to his redundant. When he decided to ditch his AGA, he was comfortable, confident and he did exactly as his training taught him.
When diver A switched to his redundant air source, if for any reason there was a failure with the secondary air source, he could have switched back to the AGA which was free flowing, but usable, this is also a skill taught in the Open Water AGA Training course.
Once on the surface, it was important to stop the free flow by disconnecting the mask before the primary tank was empty. This ensured there was enough air left to power inflate the BCD. Otherwise the diver would have had to manually inflate the BCD.
Contact with Dr. Zenetti was initiated by the Marine Unit Training Board, at the beginning of the training, to establish the proper procedures for notifying and transporting an injured diver. Having established this contact prior to an incident helped assisted in calling the doctor on his personal cell phone and making arrangements for him to see the divers.
Checking the Nut to ensure it is finger tight has been included in the Pre-Dive Checklist. The tightness of the nut will be checked by the diver and the tender prior to entering the water.
